Mechanics of the Segmentation of an Embedded Fiber, Part II: Computational Modeling and Comparisons

1995 ◽  
Vol 62 (1) ◽  
pp. 98-107 ◽  
Author(s):  
A. P. S. Selvadurai ◽  
A. ten Busschen
Keyword(s):  
Numerical Modeling ◽  
Crack Extension ◽  
Numerical Models ◽  
Matrix Cracking ◽  
Fragmentation Test ◽  
Static Crack ◽  
Reinforcing Fibers ◽  
The Matrix ◽  
Matrix Region ◽  
Elastic Fracture

A fragmentation test has been developed for the study of the influence of the adhesive characteristics of the interface between reinforcing fibers and the matrix on the development of matrix cracking at a cracked single fiber location. The present paper examines the numerical modeling of the crack extension process within the matrix region. The numerical modeling focuses on the application of boundary element techniques to the study of an axisymmetric fiber-matrix model and quasi-static crack extension criteria are employed to determine the path of crack extension. The result for the crack extension patterns obtained from the numerical models are compared with the results derived from the experiments. It is shown that elastic fracture mechanics simulations of quasi-static crack extension can successfully model the observed experimental phenomena.

Mechanics of the Segmentation of an Embedded Fiber, Part I: Experimental Investigations

1995 ◽  
Vol 62 (1) ◽  
pp. 87-97 ◽  
Author(s):  
A. ten Busschen ◽  
A. P. S. Selvadurai
Keyword(s):  
Structural Parameters ◽  
Matrix Material ◽  
Micromechanical Modeling ◽  
Experimental Investigations ◽  
Shear Stresses ◽  
Research Attention ◽  
Fragmentation Test ◽  
The Matrix ◽  
Matrix Region ◽  
Interface Bond

Micromechanical modeling is an important aspect in the study of fiber-reinforced composites. In such studies, an important class of structural parameters is formed by the interaction between the matrix and the embedded fibers. These interactive processes can be investigated by an appeal to a test which involves the segmentation of an embedded fiber. This test is referred to as a “fragmentation test.” During a fragmentation test, two distinct fracture phenomena are observed. These phenomena are directly related to the integrity of bond between the embedded fiber and the matrix. The first phenomenon involves situations where the interface bond is weaker than the matrix material. In this case the fiber fragment ends will slip and in this region shear stresses are transmitted by friction and/or interlocking mechanical actions. In contrast, when the interface bond has stronger properties than the matrix material, cracking will occur in the matrix region. Here, a crack initiated in the fiber will propagate into the matrix region typically forming conoidal cracks, or combinations of conoidal and flat cracks. This paper describes the background of the fragmentation test and the associated experimental research. Attention is focused on the experimental evaluation of matrix fracture topographies encountered in the fragmentation test.

SOME PROBLEMS OF NANOPROBE MODELING

2009 ◽  
Vol 24 (05) ◽  
pp. 799-815
Author(s):  
SERGE N. ANDRIANOV ◽  
NIKOLAY S. EDAMENKO ◽  
YURY V. TERESHONKOV
Keyword(s):  
Numerical Modeling ◽  
Nonlinear Models ◽  
Numerical Models ◽  
Nonlinear Effects ◽  
Research Process ◽  
Matrix Formalism ◽  
Modeling Process ◽  
The Matrix ◽  
Solution Methods ◽  
Beam Characteristics

We treat here the process of simulation of ion micro- and nanoprobes in detail using the matrix formalism for Lie algebraic tools. Similar approach allows realizing necessary analytical and numerical modeling procedures. Nowadays ion micro- and nanoprobes are extensively applied in different branches of science and industry. It is known that similar facilities are very sensitive to certain of steering parameters of the systems. In other words, similar beam lines are high precision systems, requiring preliminary modeling for thorough analysis of possible optimal working regimes. In this paper we consider analytical and numerical models, which allow one to study effect of various aberrations on basic beam characteristics. Research process performs from linear to nonlinear model with step by step including nonlinear effects of different nature. Previous papers of the authors consider some aspects of nonlinear models. The present paper deals with full conception of modeling process, generalizing most essential aberrations and providing adequate solution methods.

scholarly journals Two-Dimensional Numerical Modeling of Flow in Physical Models of Rock Vane and Bendway Weir Configurations

Water ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 458
Author(s):  
Drew C. Baird ◽  
Benjamin Abban ◽  
S. Michael Scurlock ◽  
Steven B. Abt ◽  
Christopher I. Thornton
Keyword(s):  
Numerical Modeling ◽  
Physical Model ◽  
Numerical Models ◽  
Hydraulic Performance ◽  
Physical Models ◽  
Protection Measures ◽  
Design Engineers ◽  
Model Study ◽  
Study Results ◽  
Wide Range

While there are a wide range of design recommendations for using rock vanes and bendway weirs as streambank protection measures, no comprehensive, standard approach is currently available for design engineers to evaluate their hydraulic performance before construction. This study investigates using 2D numerical modeling as an option for predicting the hydraulic performance of rock vane and bendway weir structure designs for streambank protection. We used the Sedimentation and River Hydraulics (SRH)-2D depth-averaged numerical model to simulate flows around rock vane and bendway weir installations that were previously examined as part of a physical model study and that had water surface elevation and velocity observations. Overall, SRH-2D predicted the same general flow patterns as the physical model, but over- and underpredicted the flow velocity in some areas. These over- and underpredictions could be primarily attributed to the assumption of negligible vertical velocities. Nonetheless, the point differences between the predicted and observed velocities generally ranged from 15 to 25%, with some exceptions. The results showed that 2D numerical models could provide adequate insight into the hydraulic performance of rock vanes and bendway weirs. Accordingly, design guidance and implications of the study results are presented for design engineers.

Effect of temperature on matrix multicracking evolution of C/SiC fiber-reinforced ceramic-matrix composites

2020 ◽  
Vol 39 (1) ◽  
pp. 189-199
Author(s):  
Longbiao Li
Keyword(s):  
Strain Energy ◽  
Ceramic Matrix Composites ◽  
Critical Value ◽  
Matrix Cracking ◽  
Interface Debonding ◽  
Matrix Composites ◽  
Temperature Dependent ◽  
Damage State ◽  
The Matrix ◽  
Sic Composites

AbstractIn this paper, the temperature-dependent matrix multicracking evolution of carbon-fiber-reinforced silicon carbide ceramic-matrix composites (C/SiC CMCs) is investigated. The temperature-dependent composite microstress field is obtained by combining the shear-lag model and temperature-dependent material properties and damage models. The critical matrix strain energy criterion assumes that the strain energy in the matrix has a critical value. With increasing applied stress, when the matrix strain energy is higher than the critical value, more matrix cracks and interface debonding occur to dissipate the additional energy. Based on the composite damage state, the temperature-dependent matrix strain energy and its critical value are obtained. The relationships among applied stress, matrix cracking state, interface damage state, and environmental temperature are established. The effects of interfacial properties, material properties, and environmental temperature on temperature-dependent matrix multiple fracture evolution of C/SiC composites are analyzed. The experimental evolution of matrix multiple fracture and fraction of the interface debonding of C/SiC composites at elevated temperatures are predicted. When the interface shear stress increases, the debonding resistance at the interface increases, leading to the decrease of the debonding fraction at the interface, and the stress transfer capacity between the fiber and the matrix increases, leading to the higher first matrix cracking stress, saturation matrix cracking stress, and saturation matrix cracking density.

Stochastic Aspects of Matrix Cracking in Brittle Matrix Composites

1993 ◽  
Vol 115 (3) ◽  
pp. 314-318 ◽  
Author(s):  
S. M. Spearing ◽  
F. W. Zok
Keyword(s):  
Matrix Cracking ◽  
Matrix Composites ◽  
Brittle Matrix ◽  
Tensile Response ◽  
Brittle Matrix Composites ◽  
Crack Interactions ◽  
The Matrix ◽  
Interface Slip ◽  
Bridging Fibers

A computer simulation of multiple cracking in fiber-reinforced brittle matrix composites has been conducted, with emphasis on the role of the matrix flaw distribution. The simulations incorporate the effect of bridging fibers on the stress required for cracking. Both short and long (steady-state) flaws are considered. Furthermore, the effects of crack interactions (through the overlap of interface slip lengths) are incorporated. The influence of the crack distribution on the tensile response of such composites is also examined.

STRUCTURING OF CURED POLYMERIC COMPOSITE MATERIALS IN A MICROWAVE ELECTROMAGNETIC FIELD

2021 ◽  
pp. 3-9
Author(s):  
I. V. Zlobina
Keyword(s):  
Electromagnetic Field ◽  
Composite Materials ◽  
Polymer Composite ◽  
Contact Interaction ◽  
Energy Systems ◽  
Polymeric Composite ◽  
Strength Characteristics ◽  
Polymer Composite Materials ◽  
Reinforcing Fibers ◽  
The Matrix

Based on studies of the microstructure of the matrix of cured polymer composite materials and the area of its contact interaction with reinforcing fibers, the hypothesis of its structuring in the microwave electromagnetic field with an increase in the contact interaction surfaces due to an increase in the number of agglomerates with small transverse dimensions and a decrease in porosity in the macro- and mesopore regions is substantiated. These effects can be used as a basis for increasing the strength characteristics and uniformity of their values after exposure to a microwave electromagnetic field. The results of this work can be used in the development of technologies for finishing hardening of products made of carbon and fiberglass for various transport and energy systems.

scholarly journals Numerical modeling of the hydraulic impact of riparian vegetation

2018 ◽  
Vol 44 ◽  
pp. 00194
Author(s):  
Krzysztof Wolski ◽  
Tomasz Tymiński ◽  
Grzegorz Chrobak
Keyword(s):  
Numerical Modeling ◽  
Riparian Vegetation ◽  
Water Surface ◽  
Numerical Models ◽  
Three Dimensional ◽  
Careful Examination ◽  
Impact Structure ◽  
Hydraulic Impact ◽  
Vegetation Zones ◽  
Maximal Shear Stress

This paper presents results of numerical modelling of riverbed segment with riparian vegetation performed with use of CCHE2 software. Vegetation zones are places where dynamic of water flow increases. Therefore, there is a need of careful examination of hydraulic impact structure of such zones. Accurate research is necessary and should be performed with use of physical or numerical models, two or three dimensional. Paper presents distribution of velocity and area of water surface for two variants of vegetation deposition acquired in CCHE2D software and modelled for riverbed with distinctive riparian vegetation. Results point to significant (30–40%) increase of maximal velocities in riverbed with riparian vegetation, while directly near the vegetation there were zones with very low velocities. Local damming occurs before vegetal zone. Maximal shear stress in zones with increased velocity is significantly augmented compared to conditions with no vegetation, which can cause more intensive erosion in those zones

Stress Corrosion Cracking Behavior of Uranium Alloys

CORROSION ◽  
1974 ◽  
Vol 30 (5) ◽  
pp. 181-189 ◽  
Author(s):  
W. F. CZYRKLIS ◽  
M. LEVY
Keyword(s):  
Fracture Mechanics ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Threshold Stress ◽  
Crack Extension ◽  
Corrosion Cracking ◽  
Nacl Solution ◽  
Cracking Behavior ◽  
Linear Elastic ◽  
Elastic Fracture

Abstract The stress corrosion cracking (SCC) behavior of U-3/4% Ti, and uranium alloys 3/4% Quad, 1% Quad, and 1% Quint have been studied utilizing a linear elastic fracture mechanics approach. The threshold stress intensities for stress corrosion crack propagation for these alloys have been determined in distilled H2O and NaCl solutions containing 50 ppm Cl− and 21,000 ppm Cl−. All of the alloys studied may be classified as very susceptible to SCC in aqueous solutions since they exhibit SCC in distilled H2O (<1 ppm Cl−) and have low KIscc values in NaCl solutions. Crack extension in all of the alloys in all environments was transgranular and failure occurred by brittle quasicleavage fracture in NaCl solution.

scholarly journals Numerical Modeling of a Punch Penetration Test Using the Discrete Element Method

2020 ◽  
Vol 28 (2) ◽  
pp. 1-7
Author(s):  
Rouhollah Basirat ◽  
Jafar Khademi Hamidi
Keyword(s):  
Numerical Modeling ◽  
Discrete Element Method ◽  
Numerical Models ◽  
Confining Pressure ◽  
Discrete Element ◽  
Numerical Results ◽  
Strength Parameter ◽  
Penetration Test ◽  
Strength Parameters ◽  
Element Method

AbstractUnderstanding the brittleness of rock has a crucial importance in rock engineering applications such as the mechanical excavation of rock. In this study, numerical modeling of a punch penetration test is performed using the Discrete Element Method (DEM). The Peak Strength Index (PSI) as a function of the brittleness index was calculated using the axial load and a penetration graph obtained from numerical models. In the first step, the numerical model was verified by experimental results. The results obtained from the numerical modeling showed a good agreement with those obtained from the experimental tests. The propagation path was also simulated using Voronoi meshing. The fracture was created under the indenter in the first step, and then radial fractures were propagated. The effects of confining pressure and strength parameters on the PSI were subsequently investigated. The numerical results showed that the PSI increases with enhancing the confining pressure and the strength parameter of the rock, including cohesion and the friction angle. A new relationship between the strength parameters and PSI was also introduced based on two variable regressions of the numerical results.

scholarly journals Numerical modeling of hiding properties of underwater acoUStic communication signals with linear sweep of the carrier

2020 ◽  
Author(s):  
К.Г. Кебкал
Keyword(s):  
Numerical Modeling ◽  
Continuous Spectrum ◽  
Gaussian Noise ◽  
Data Exchange ◽  
Numerical Models ◽  
Underwater Acoustic Communication ◽  
Underwater Acoustic ◽  
Communication Signals ◽  
Communication Signal ◽  
Spectrum Spread

На результатах численного моделирования продемонстрировано, что распределения вероятностей огибающей и фазы смеси гауссова шума и (слабого) гидроакустического сигнала связи, характеризуемого линейной разверткой несущей, могут иметь исчезающе малые отличия от аналогичных распределений, характерных для просто гауссова шума. Использование непрерывного расширения спектра сигнала связи может представлять интерес для задач скрытого обмена данными, в которых обнаружение сеанса связи устройствами перехвата должно быть затруднительным или невозможным. С применением численных моделей проанализированы возможности использования сигналов с непрерывным расширением спектра для скрытой цифровой гидроакустической связи посредством штатных приемоизлучающих гидроакустических систем, находящихся на вооружении действующих кораблей. Based on the results of the numerical modeling, the vanishingly small differences between the probability distributions of the envelope and phase of the sum of Gaussian noise and (weak) underwater acoustic signal with linear carrier sweep, and the same distributions for the Gaussian noise all alone are demonstrated. Utilization of the continuous spectrum spread of the communication signal may be applied to the task of covert data exchange, where detection of the communication session by the intercepting equipment must be complicated or impossible. Using numerical models, we analyzed the capabilities of implementation of the signals with continuous spectrum spread for covert digital underwater acoustic communications through the standard underwater acoustic transducers, which are in service on the operational ready vessels.

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